Mattress



FIG. 1 is a front elevational view of a mattress showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a perspective view thereof;

FIG. 8 is another perspective view thereof;

FIG. 9 is a perspective view in state of use; and,

FIG. 10 is another perspective view in state of use.

The broken lines shown in FIG. 10 form no part of the claimed design. 

CLAIM The ornamental design for a mattress, as shown and described. 